It is often desirable in computer systems to allow for upgrading or addition of various integrated circuits or printed circuit boards. For example, it is often desirable to allow various chips, such as the microprocessor, to be replaceable to provide greater performance. It is also desirable to allow additional chips such as memory chips to be added. From a user's perspective, it is preferable that upgrades be capable of being performed by untrained personnel with a minimum of tools. From a system designer's perspective, the capability for additional or different parts must be designed into the system. In particular, with respect to additional parts such as memory chips or cards, careful consideration must be given to the placement of such chips or cards to ensure timing requirements are met. Such timing requirements are particularly stringent for high-performance systems that operate at high clock rates.
Add-in cards, which comprise one or more integrated circuits on a printed circuit board offer a well known component add-in capability. An example of such an add-in card is described in U.S. Pat. No. 4,656,605 to Clayton entitled "Single In-Line Memory Module." Increasingly, there is a need to allow addition or replacement of additional chips, as the functions performed on cards become integrated into single chips. Ideally, such chips should be user installable, and require little or no tools or specialized knowledge.